EP11.03 EMERGENCY STEREOTACTIC RADIOSURGERY FOR SOLITARY BRAINSTEM METASTASIS IN CERVICAL CANCER: A NOVEL APPLICATION OF GYROSCOPIC RADIOTHERAPY

Abstract BACKGROUND Metastases of cervical squamous cell carcinoma (SCC) to the brain are exceedingly rare, and those affecting the brainstem are even more exceptional. Their anatomical complexity limits surgical access and therapeutic options. The ZAP-X radiosurgery system, employing a self-shielded gyroscopic linear accelerator, offers high-precision stereotactic radiosurgery (SRS) particularly suitable for treating lesions in eloquent brain areas. MATERIAL AND METHODS We report a case of a 49-year-old female patient with FIGO stage IIB HPV-associated cervical SCC, initially treated with definitive chemoradiotherapy and brachytherapy. Fifteen months after completion of treatment, she developed neurological symptoms indicative of central nervous system involvement. MRI revealed a solitary contrast-enhancing lesion in the dorsal pons. A multidisciplinary team indicated SRS with ZAP-X. The patient underwent single-fraction ZAP-X treatment to 18 Gy at the 50% isodose line. RESULTS The treatment was well tolerated with no acute complications. The patient experienced symptomatic improvement in balance and vision. Ophthalmologic follow-up confirmed resolution of a left abducens nerve palsy. Follow-up MRI at six weeks post-treatment demonstrated a reduction in lesion volume by approximately 35%, with decreased perilesional edema and no new CNS or systemic lesions. CONCLUSION This is one of the first reported cases of a solitary brainstem metastasis from cervical SCC treated using the ZAP-X system. The favorable clinical and radiological outcomes support its use as a safe and effective modality for managing intracranial metastases in anatomically sensitive regions. ZAP-X SRS may expand the therapeutic options available for rare and complex CNS metastases in gynecologic oncology.